The present invention relates generally to devices used in the propagation of plants, and in particular to a device for use in germinating and growing plants.
In the horticultural industry, it is common practice to germinate seedlings or cultivate young plants in containers or trays having a plurality of like sized cavities or cells, each of which is dimensioned to receive a charge of plant growing material, such as peat moss, soil and the like, and one or more seeds or young plants. These trays, commonly referred to as xe2x80x9cplug traysxe2x80x9d within the industry, normally have the cells arranged in a closely packed, uniform spatial array such that a maximum number of plants may be grown within each tray. Once the seeds or young plants and the material necessary for growth are positioned within the cells, the plug tray is positioned in a designated area and exposed to environmental conditions necessary for expedient plant growth. Once the plants within the plug tray cells achieve a certain amount of growth, or have been positioned within the plug tray for a preselected period of time, the plants are removed from the plug tray and transplanted into larger containers.
Normally, both the placement of the seeds and growing material within the cells, and the transplantation of plants from the plug tray into larger containers, is accomplished by an automated process. In this automated process, the plug trays are placed in a contiguous end-to-end relationship along a conveying surface. The plug trays are filled with growing media as they move on a conveyor. An automated device, positioned above the plug trays, deposits one or more seeds into the cells, or removes the plants together with the xe2x80x9croot plugxe2x80x9d or xe2x80x9croot systemxe2x80x9d contained within each cell and deposits the same in a larger container. The automated device is positioned overhead of the plug trays and is formed having a plurality of laterally extending fingers or guides which are moved into position below the top surface of the plug tray, and between the cells. These lateral guides align the plug tray below the automated device. The automated device is calibrated to descend upon a particular cell or cells within the plug tray based upon the center-to-enter distance between adjacent cells. Consequently, it is critical for the effective and efficient operation of this automated process that the center-to-center distances between adjacent cells of the plug trays is maintained.
In the past, it has been common practice to use a single plug tray in the deposition and transplantation processes. However, when using multiple plug trays, a difficulty encountered by the industry is the ineffective deposition into, and transplantation from, a series of plug trays due to the non-uniformity in the center-to-center distance between cells of adjacent plug trays. That is, at the intersection between two adjacent plug trays, the center-to-center distance between the cells of the last row of one plug tray and the first row of the second plug tray are not equal to the center-to-center distance between the remainder of the cells composing a particular plug tray. Consequently, when the automated device descends upon the first row of cells of a second plug tray, the automated device often fails to adequately align with the center of the cell. This lack of centering between the automated device and the cells of a plug tray results in the failure to deposit the seed within the cell, or in the case of transplantation, to adequately grasp the entirety of the plant and its root system. This in turn causes ineffective filling of the plug tray cells, and when transplanting, increases the likelihood of damage to the plants and/or plug tray, and reduces the efficiency of the transplantation process. Furthermore, the inefficiencies caused by non-uniform center-to-center distances between plug trays will continue until the automated device is shut down and the plug trays are repositioned.
Heretofore, the use of multiple plug trays in the automated processes previously described has required the plug trays to have vertical exterior walls in order to maintain a uniform distance between the cells of adjacent plug trays. Additionally, some plug trays are designed and manufactured to be reusable. One method commonly used to form a reusable plug tray having vertical exterior walls is injection molding. Injection molding is a relatively expensive molding process, and hence increases the manufacturing costs and can add complications to the plug growing process.
Reusing plug trays presents additional problems within the industry. Specifically, reusing plug trays exposes the second or successive batch of plants to potential disease from the previous plant batch. Thus, in many instances, to prevent transmission of plant diseases, the reusable plug trays are cleaned before accepting another batch of seed. Cleaning the plug trays is a cumbersome procedure which increases the complexity and costs of the plant cultivation procedure. Specifically, cleaning the plug trays requires the purchase of a relatively expensive cleaning/sterilizing apparatus.
Accordingly, there exists a need within the industry for a plug tray which overcomes the difficulties of the prior art by providing a uniform center-to-center distance between the cells of adjacent plug trays, which is sufficiently economical to manufacture so as to avoid the need for reuse, is recyclable, and exhibits the requisite strength and rigidity for both singular tray or multiple tray use, and especially with automated processes.
The present invention provides a plug tray having increased strength and rigidity which may be manufactured using the relatively inexpensive thermoforming process. By employing the thermoforming process, it becomes economically feasible to use the plug tray of the present invention in the cultivation of a single batch of seeds or young plants, whereafter the plug tray may be recycled. Providing an economical, single use plug tray reduces the potential for disease in successive batches of plants and eliminates the need to clean the plug tray subsequent to transplantation. Furthermore, the plug tray of present invention is configured having a uniform center-to-center distance between the cells of adjacent plug trays, which in turn maximizes the efficiency of the automated planting and transplantation processes.
According to an aspect of the invention, a plug tray for growing plants includes a surface member having formed in or therethrough a plurality of rows of inner cavities or cells, and a pair of rows of outer cells with each row of outer cells adjacent to an end of the surface member. Each cell is dimensioned to accept a charge of growing material, and at least one seed or young plant. A plurality of apertures are formed in the surface member to thereby provide aeration for plant growth. The apertures are formed in the surface member such that each aperture is separated from the cells by the surface member. Each inner and outer cell is at a preselected offset angle with respect to the major axis of the surface member. Offsetting the cells at a preselected angle yields a plug tray having greater strength and rigidity, and thus enables the plug tray to be manufactured using the less expensive method of thermoforming. Further strength is gained by forming the apertures such that the surface member surrounds the apertures and separates the same from the cells. Additionally, off-setting the cells at a preselected angle provides a centering effect which aids in the alignment of the plug trays during the automated deposition and transplantation processes. Due to the off-set angle, the lateral guides of the automated device extending below the top surface of the plug tray have less clearance between adjacent rows of cells, and thereby enables the lateral guides to achieve greater precision in aligning the plug trays.
In a preferred embodiment, the plurality of apertures are positioned in rows, such that each row of inner cells is bordered by a pair of rows of apertures, while each row of outer cells is bordered by a single row of apertures. Thus, positioned adjacent each aperture are either four inner cells, or two inner cells and two outer cells. In an alternative preferred embodiment, the plurality of apertures are formed in diagonal rows such that each inner cell is adjacent to two apertures, while each outer cell is adjacent to one aperture.
According to another aspect of the invention, a plug tray includes a surface member and a plurality of rows of inner cells formed therein. Each inner cell has a substantially square shape and four sides attached to a bottom member, wherein the bottom member has a hole formed therein such that each side of the four sides is separated from the hole by the bottom member. The surface member is further formed having a plurality of apertures, preferably providing aeration. Proximate to each opposing end of the surface member is a row of outer cells. The outer cells are shaped with a top opening edge proximate to, and generally parallel with, an end of the surface member. The generally parallel top opening edge of each outer cell permits the plug tray of the instant invention to be used in a continuous planting or transplantation operation wherein plug trays are positioned in an adjacent end-to-end arrangement. As the distance between the outer cells of adjacent plug tray is approximately equal to the distance between the inner cells, there is a seamless transition between the plug trays when used in an automated planting and transplantation process. This in turn increases the efficiency of both the planting and transplantation process. Additionally, the substantially square shape of the cells having sides and a bottom member, wherein the hole is formed in the bottom member such that each side is separated from the hole by the bottom member, provides the advantage of supporting the bottom of the root plug, while allowing aeration. The use of a bottom member also permits the cell to have a greater area and thus increases the amount of growing material which may be inserted into each cell, hence maximizing the chances of successful plant growth.
According to still another aspect of the invention, a plug tray includes a pair of opposing ends and a pair of opposing sides, a plurality of rows of inner cells and a pair of rows of outer cells, each of which is adjacent to an end of the opposing ends. Each inner cell and outer cell is formed having four top opening edges, wherein each top opening edge is substantially parallel to either the opposing sides or opposing ends. Each inner cell and outer cell has a first dimension generally parallel to the opposing ends and a second dimension generally parallel to the opposing sides. The first dimension of each inner cell is greater than the first dimension of each outer cell and the second dimension of each inner cell is greater than the second dimension of each outer cell. Providing a plurality of inner cells each of which has a greater size than the outer cells permits the plug tray to be used in automation deposition and transplantation processes because the center-to-center distance between the outer cells of adjacent plug trays is substantially the same as the center-to-center distance between the inner cells of the tray. Furthermore, providing a plug tray having cells with four top opening edges, each of which is substantially parallel to either the opposing sides or opposing ends, enables the maximization of the number of cells within the tray.
According to yet another aspect of the invention, a method of forming a plug tray includes thermoforming a polymer sheet into a plug tray including a surface member having a perimeter defined by a pair of opposing sides, a pair of opposing ends, and having a major axis, and a plurality of rows of cells formed in said surface member. Employing a thermoforming process in the manufacture of plug trays significantly reduces manufacturing costs and thereby enables the plug tray of the present invention to be used in the cultivation of a single batch of plants, and subsequently recycled.
According to still yet another aspect of the invention, a system for growing plants includes a first and second plug tray wherein an end of the first plug tray is positioned in contact with the end of the second plug tray. Each plug tray includes a surface member formed with a plurality of rows of inner cells, apertures and a pair of rows of outer cells. Each outer cell is formed so that the center-to-center distance between the outer cells of the plug trays is substantially equal to the center-to-center distance between adjacent inner cells, to thereby enable the system to be used in conjunction with automated processes.
These and other objects, advantages, purposes and features of the invention will become apparent upon review of the following specification in conjunction with the drawings.